Figure 3.

Behavioral effects of varying sensorimotor demands of grasping by object slant. A–F, Bar plots showing kinematic parameter values of the effect of object slant (mean ± SEM). Color coding is as in Figure 1, B and C: bars are grouped by object slant (blue, vertical; orange, horizontal), with bar face color indicating the site of TMS (gray, control; magenta, aIPS; cyan, sPOS). Significant effects of object slant are indicated with stars (*0.01 < p < 0.05; **p < 0.001). A, RTs were not modulated by object slant, but were significantly shorter after TMS over aIPS compared with control stimulation. B, Grasping movement durations increased with increasing object slant. C, D, The increase in movement duration was driven by an increased TL and accompanied by a small increase in their PV. E, F, During the transport toward the object (first 75% of the movement) the velocity of the virtual grip sensor increased with increasing object slant (μTV). In contrast, when approaching near horizontal objects (last 25% of the movement) the fingers moved with a slower velocity than when approaching near vertical objects (μAV). G, H, The PGA was smaller and occurred later (tPGA) when grasping more horizontally oriented objects.